Question

How does diffraction affect radio signals?

Answer 1

Same as for light. See below.

Explanation:

Remember radio waves or signals is the same as light waves.

Light is just a small fraction of the entire spectrum of the electromagnetic waves.

In the case of light, diffraction causes it to bend around corners of an obstacle, you would have a similar phenomena woth radio signals, but the "radius" of bend would be far larger on account of the larger wavelengths of the radio signals.